In recent years, from the standpoint of ecological aspects such as saving in space and power, commercial products, which adopt liquid crystal panels or organic electroluminescence (EL) panels as display devices, have been gaining in popularity, as typified by liquid crystal monitors, liquid crystal televisions, mobile phones, smartphones, tablets, electronic books, and notebook-type personal computers. In particular, in various kinds of electronic devices such as smartphones, tablets, electronic books and mobile phones, use is made of touch panels which can input position information by touching on screen surfaces thereof with use of fingers or the like, and cover glasses which cover outer peripheral parts other than screen display parts, as well as the display panels such as liquid crystal panels and organic EL panels.
As a technique of attaching thin plates such as a display panel, a touch panel and a cover glass, there is known a technique in which an ultraviolet-curing resin is coated on the surface of one thin plate, the other thin plate is laid over the one thin plate, and the resin is cured by ultraviolet irradiation after the resin has spread up to a necessary filling area.
In the meantime, taking into account the suppression of variance in amount of the resin that is coated, or the suppression of bubbles, for instance, it is difficult to restrict the area, where the resin is to be filled, to only a display area (hereinafter referred to as “active area”) which displays an image. Consequently, there is a case in which the filling area of resin extends outside the active area and reaches the outer peripheral part of the cover glass, which is covered with, for example, a light-shield layer which hardly passes light. In such a case, in the filling area of resin, an area, where ultraviolet that is necessary for curing does not easily reach, will occur under the light-shield layer. In such an area, it is possible that the spreading of the non-cured resin cannot be suppressed, and the resin protrudes to the outside of the display panel.
In particular, as regards smartphones and tablets, technical development has been promoted for specifications of a “narrow picture frame” that is a market demand, in order to achieve both the reduction in size and the enlargement of an active-area screen and to thereby accomplish their task for uses as mobile equipment. Thus, as regards the display panel, since the width of a peripheral area on the outside of the active area has become narrower, it is more important to stem the spreading of the resin at the peripheral area. The resin protruding to the outside of the display panel becomes a hinder when the display panel is assembled in an electronic device body, and may lead to degradation in quality. Moreover, in a step of removing the protruding resin, the removed resin becomes a contaminant, leading to a factor of degradation in quality.